Portrait of Boston Red Sox legend Ted Williams Sarasota, Florida

In baseball statistics, on-base percentage (OBP) measures how frequently a batter reaches base. An official

Major League Baseball Major League Baseball (MLB) is a professional baseball organization and the oldest major professional sports league in the world. MLB is composed of 30 total teams, divided equally between the National League (NL) and the American League (A ...

(MLB) statistic since 1984, it is sometimes referred to as on-base average (OBA), as it is rarely presented as a true

percentage In mathematics, a percentage (from la, per centum, "by a hundred") is a number or ratio expressed as a fraction of 100. It is often denoted using the percent sign, "%", although the abbreviations "pct.", "pct" and sometimes "pc" are also use ...

. Generally defined as "how frequently a batter reaches base per

plate appearance In baseball statistics, a player is credited with a plate appearance (denoted by PA) each time he completes a turn batting. Under Rule 5.04(c) of the Official Baseball Rules, a player completes a turn batting when he is put out or becomes a runn ...

", OBP is specifically calculated as the ratio of a batter's

times on base In baseball statistics, the term times on base (TOB), is the cumulative total number of times a batter has reached base as a result of a hit, base on balls, or hit by pitch. This statistic does not include times reaching base by way of an error ...

(the sum of

hit Hit means to strike someone or something. Hit or HIT may also refer to: Arts, entertainment and media Fictional entities * Hit, a fictional character from '' Dragon Ball Super'' * Homicide International Trust, or HIT, a fictional organization ...

bases on balls A base on balls (BB), also known as a walk, occurs in baseball when a batter receives four pitches that the umpire calls '' balls'', and is in turn awarded first base without the possibility of being called out. The base on balls is defined in Sec ...

, and times

hit by pitch In baseball, hit by pitch (HBP) is an event in which a batter or his clothing or equipment (other than his bat) is struck directly by a pitch from the pitcher; the batter is called a hit batsman (HB). A hit batsman is awarded first base, provided ...

) to the sum of

at bat In baseball, an at bat (AB) or time at bat is a batter's turn batting against a pitcher. An at bat is different from a plate appearance. A batter is credited with a plate appearance regardless of what happens during their turn at bat, but a batt ...

s, bases on balls, hit by pitch, and

sacrifice flies In baseball, a sacrifice fly (sometimes abbreviated to sac fly) is defined by Rule 9.08(d): "Score a sacrifice fly when, before two are out, the batter hits a ball in flight handled by an outfielder or an infielder running in the outfield in fair o ...

. OBP does not credit the batter for reaching base on fielding errors,

fielder's choice In baseball, fielder's choice (abbreviated FC) refers to a variety of plays involving an offensive player reaching a base due to the defense's attempt to put out another baserunner, or the defensive team's indifference to his advance. Fielder's choi ...

uncaught third strike In baseball and softball, an uncaught third strike (sometimes referred to as dropped third strike or non-caught third strike) occurs when the catcher fails to cleanly catch a pitch for the third strike of a plate appearance. In Major League Ba ...

s, fielder's obstruction, or

catcher's interference In baseball, interference occurs in situations in which a person illegally changes the course of play from what is expected. Interference might be committed by players on the offense, players not currently in the game, catchers, umpires, or spec ...

. OBP is added to

slugging average In baseball statistics, slugging percentage (SLG) is a measure of the batting productivity of a hitter. It is calculated as total bases divided by at bats, through the following formula, where ''AB'' is the number of at bats for a given player, ...

(SLG) to determine on-base plus slugging (OPS). The OBP of all batters faced by one pitcher or team is referred to as "on-base against". On-base percentage is calculable for professional teams dating back to the first year of National Association of Professional Base Ball Players competition in 1871, because the component values of its formula have been recorded in box scores ever since.

History

The statistic was invented in the late 1940s by Brooklyn Dodgers statistician Allan Roth with then-Dodgers general manager Branch Rickey. In 1954, Rickey, who was then the general manager of the

Pittsburgh Pirates The Pittsburgh Pirates are an American professional baseball team based in Pittsburgh. The Pirates compete in Major League Baseball (MLB) as a member club of the National League (NL) Central division. Founded as part of the American Associati ...

, was featured in a

Life Magazine ''Life'' was an American magazine published weekly from 1883 to 1972, as an intermittent "special" until 1978, and as a monthly from 1978 until 2000. During its golden age from 1936 to 1972, ''Life'' was a wide-ranging weekly general-interest ma ...

graphic in which the formula for on-base percentage was shown as the first component of an all-encompassing "offense" equation. However, it was not named as on-base percentage, and there is little evidence that Roth's statistic was taken seriously at the time by the baseball community at large. On-base percentage became an official MLB statistic in 1984. Its perceived importance jumped after the influential 2003 book '' Moneyball'' highlighted

Oakland Athletics The Oakland Athletics (often referred to as the A's) are an American professional baseball team based in Oakland, California. The Athletics compete in Major League Baseball (MLB) as a member club of the American League (AL) West division. The t ...

general manager Billy Beane's focus on the statistic. Many baseball observers, particularly those influenced by the field of

sabermetrics Sabermetrics, or originally SABRmetrics, is the empirical analysis of baseball, especially baseball statistics that measure in-game activity. Sabermetricians collect and summarize the relevant data from this in-game activity to answer specific que ...

, now consider on-base percentage superior to the statistic traditionally used to measure offensive skill, batting average, which accounts for hits but ignores other ways a batter can reach base.

Overview

Traditionally, players with the best on-base percentages bat as

leadoff hitter In baseball, a leadoff hitter is a batter who bats first in the lineup. It can also refer to any batter who bats first in any inning. Strategy Traditionally, the leadoff hitter has been utilized as a contact-oriented position. The leadoff hit ...

, unless they are power hitters, who traditionally bat slightly lower in the batting order. The league average for on-base percentage in

has varied considerably over time; at its peak in the late 1990s, it was around .340, whereas it was typically .300 during the dead-ball era. On-base percentage can also vary quite considerably from player to player. The highest career OBP of a batter with more than 3,000

s is .482 by

Ted Williams Theodore Samuel Williams (August 30, 1918 – July 5, 2002) was an American professional baseball player and manager. He played his entire 19-year Major League Baseball (MLB) career, primarily as a left fielder, for the Boston Red Sox from 193 ...

. The lowest is by Bill Bergen, who had an OBP of .194. On-base percentage is calculated using this formula: :

OBP = \frac

where *''H'' =

Hits Hits or H.I.T.S. may refer to: Arts, entertainment, and media Music * '' H.I.T.S.'', 1991 album by New Kids on the Block * ''...Hits'' (Phil Collins album), 1998 * ''Hits'' (compilation series), 1984–2006; 2014 - a British compilation album s ...

*''BB'' = Bases on Balls (Walks) *''HBP'' =

Hit By Pitch In baseball, hit by pitch (HBP) is an event in which a batter or his clothing or equipment (other than his bat) is struck directly by a pitch from the pitcher; the batter is called a hit batsman (HB). A hit batsman is awarded first base, provided ...

*''AB'' =

At bat In baseball, an at bat (AB) or time at bat is a batter's turn batting against a pitcher. An at bat is different from a plate appearance. A batter is credited with a plate appearance regardless of what happens during their turn at bat, but a batt ...

*''SF'' =

Sacrifice fly In baseball, a sacrifice fly (sometimes abbreviated to sac fly) is defined by Rule 9.08(d): "Score a sacrifice fly when, before two are out, the batter hits a ball in flight handled by an outfielder or an infielder running in the outfield in fair o ...

In certain unofficial calculations, the denominator is simplified and replaced by

Plate Appearance In baseball statistics, a player is credited with a plate appearance (denoted by PA) each time he completes a turn batting. Under Rule 5.04(c) of the Official Baseball Rules, a player completes a turn batting when he is put out or becomes a runn ...

(PA); however, the calculation PAs includes certain infrequent events that will slightly lower the calculated OBP (i.e.

, and

sacrifice bunt In baseball, a sacrifice bunt (also called a sacrifice hit) is a batter's act of deliberately bunting the ball, before there are two outs, in a manner that allows a baserunner to advance to another base. The batter is almost always put out, and ...

s). Sacrifice bunts are excluded from consideration on the basis that they are usually imposed by the manager with the expectation that the batter will not reach base, and thus do not accurately reflect the batter's ability to reach base when attempting to do so. This is in contrast with the sacrifice fly, which is generally unintentional; the batter was trying for a hit.

All-time leaders

Single-season leaders

Notes

References